For many years the commonly used light bulb has consisted of little more than a clear or diffusing glass globe surrounding a compact light source. Reflector lamps have been provided with on-axis spherical, paraboloidal or elipsoidal reflectors to produce various beam widths. Control of the direct horizontal disability glare in lighting fixtures is commonly specified as a requirement in terms of VCP (Visual Comfort Probability). Similarly, reflected glare from near-vertical light striking a task surface has been specified in commercial lighting fixtures in terms of ESI (Equivalent Sphere Illumination). Both VCP and ESI characteristics have been relegated to light fixture designers and are therefore simply ignored by the designers and manufacturers of light bulbs. Since the ordinary incandescent light bulb by far the most common light source in residential lighting, there is little or no control over the photometric properties of the lighting in virtually every home. A typical example is the ordinary table lamp, in which a light bulb with spherical light destribution is placed within a shade that limits horizontal brightness and diffusely reflects some light downwards. If the shade has high transmissivity and efficiency the horizontal brightness is excessive, providing VCP so visually disabling that it would violate lighting standards for offices or schools. If the shade is has low transmissivity the lamp is a very inefficient room light, and the small circle of light near the base creates reflected glare. In this case the inefficiency and reflected glare would be unacceptable for business or schools, but is the state of the art in nearly every home.
The purpose of the present invention is to provide a highly efficient light bulb that will profuce precisely controlled light distribution, with low horizontal brightness for high Visual Comfort Probability and low vertical reflected glare for improved Equivalent Sphere Illumination. A purpose of one preferred embodyment is to substantially remove the infra-red energy from the reflected beam by allowing it to pass through the reflector and thereby permit a cooler illuminated area.